#include<bits/stdc++.h>

using namespace std;
using ll = long long;


int main()
{
    int n, k; cin >> n >> k;
    if(n & 1) {
        //int front = min((k % 2 == 1 ? n / 2 : (n + 1) / 2), );
        int front = (k + 2) / 2;
        int back = (k + 1) / 2;
        //int back =  min((k % 2 == 1 ? (n + 1) / 2 : n / 2), (k % 2 ? k : k - 1));
        cout << min(n, front + back) << endl;
    } else {
        int front = (k + 2) / 2;
        int back = (k + 1) / 2;
        cout << min(n / 2, front + back) << endl;
    }
}